What this means
The IEEE assigned the MA-L block 0050D9 to ENGETRON-ENGENHARIA ELETRONICA IND. e COM. LTDA. Every network interface they manufacture under this block has a MAC address beginning with these digits, followed by a unique per-device identifier. If a device on your network shows a MAC starting 00:50:D9, it is ENGETRON-ENGENHARIA ELETRONICA IND. e COM. LTDA hardware.